1558-1748 (c) 2017 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2017.2723041, IEEE Sensors Journal Abstract—Measuring and controlling torque in rotary systems is essential to preventing wear, damage, breakage and other machine malfunctions caused by excessive shaft torque. The classical methods and those currently available on the market utilize systems that must be electrically powered and for which their data must be acquired by collector rings, transformers or telemetry systems. This study develops a torque transducer for rotating shafts using a new approach that utilizes neodymium magnets and Hall effect sensors. A pair of magnets is attached to the rotating shaft, and a magnetic field measurement system with Hall effect sensors is positioned in a stationary unit close to the shaft. The relative movement between the magnets due to deformation resulting from torsion will increase or decrease the magnetic field strength. By measuring the strength of this resulting field, it is possible to determine the radial deformation of the shaft. Dynamic tests were performed in the laboratory to validate this technique and to compare it with widespread industrial techniques. The results show the efficacy of the technique and point to potential applications of this dynamic torque sensor using the Hall effect. Index Terms - torque measurement, Hall effect, permanent magnets, rotary shafts, instrumentation I. INTRODUCTION irtually all electromechanical conversion systems use rotating shafts; in these systems, torque measurements are the main parameter used to monitor safe operation and to prevent disasters in production systems [1]. The torque measurement of a rotating shaft is essential for assembling This work was supported in part by National Council for Scientific and Technological Development (CNPq). Jacques C. S. Borges was with Graduate Program in Mechanical Engineering of Federal University of Paraíba He is now with Federal Institute of Education, Science and Technology of Rio Grande do Norte, Natal, Brazil (e-mail: cousteau.borges@ifrn.edu.br). Danielson B. B. de Deus is a graduate fellow of the Petrobras Human Resources Training Program, of the Mechanical Engineering course at the Federal University of Paraiba, João Pessoa, Brazil (e-mail: danyelsonbb10@hotmail.com). Abel C. Lima Filho is with the Mechanical Engineering Department , Federal University of Paraíba, João Pessoa, Brazil (e-mail: abelima@gmail.com). Francisco A. Belo is with the Electrical Engineering Department , Federal University of Paraíba, João Pessoa, Brazil. (e-mail: belo@les.ufpb.br). machines precisely, improving machine performance and controlling power transmission systems. The main challenge for measuring the torque on rotating shafts is extracting this information from the moving shaft without interfering with the process. Currently, in the state-of- the-art research, there are three basic ways to measure the torque on rotating shafts: using passive sensors, using active sensors, and measuring the torsion angle. The passive sensors used in torque transduction can be resistive (i.e., using strain gauges) [2] [3] [4], capacitive [5], or inductive [6]. Surface acoustic wave (SAW) [7] or surface transverse wave (STW) [7] resonators have also been used. These types of torque sensors need a system to supply electricity to the circuit embedded along the shaft and to transmit information from the rotating shaft to a stationary unit. The electrical supply for the circuit on the shaft can be batteries or power transmission from a stationary source that makes contact with the rotating shaft (slip rings) [2] [8] or does not make contact (rotary transformers) [9]. The information obtained by the sensor can be transmitted via infrared [10], a radio frequency (RF) link [4] [11] [12], slip rings [2] or rotary transformers [9]. Few studies in the literature use active sensors to measure torque on rotating shafts; piezoelectric materials [13] [14] and magnetostrictive sensors [16-20] are the most common, although sensors using mechanoluminescence [15] can also be found. Transducers that estimate torque from the torsion angle may use capacitive [21], magnetic [22] or optical [23] sensors for this purpose. The oldest method is measuring torque using passive elements, and this is perhaps the most commercially used method. However, the main drawback of this method is that it relies on a circuit embedded in the rotating shaft for the preconditioning of the torque signal and information transmission; this circuit can be a source of noise, especially those circuits that use coupling with a stationary unit by contact. In addition, the sensors used as strain gauges [4] and SAW [11] generally have low resistance to abrasive environments. Torque transducers that use active sensors and torsion angle measurement do not require electronic systems attached to the rotating shafts and generally have greater noise immunity. These transducers can, for example [24], measure only the time interval between two distant magnets passing near the Hall sensor during rotation and measure the torsion angle using the magnet displacement due to the influence of torque; this method is best utilized in long axes. The disadvantage of Jacques C. S. Borges, Danielson B. B. de Deus, Abel C. Lima Filho and Francisco A. Belo New Contactless Torque Sensor Based on the Hall Effect V